JPH08205693A - Paper mulching sheet - Google Patents

Abstract

PURPOSE: To prepare a paper mulching sheet having a ground temperature-rising effect, excellent in workability, weather resistance and rotting resistance on the mechanical spreading of the mulching sheet, and useful for agriculture, etc., by providing a moisture-preventing layer on the surface of a raw paper sheet consisting mainly of natural pulp. CONSTITUTION: A paper mulching sheet wherein the thickness of a moisture- preventing layer containing a latex such as a styrene-butadiene latex and a wax such as a paraffinic wax as main components coated on its one surface is is preferably such an amount as to give a moisture permeability of <=100g/m<2> .24hr to its raw paper sheet mainly consisting of natural pulp. The raw paper sheet for the paper mulching sheet preferably has a breaking elongation of 3-20% in the longitudinal direction, and oxyquinoline (derivative) and/or fumic acid (bi or higher valency cation salt thereof) is preferably added to the raw paper sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to agricultural and horticultural paper multi-sheets, and more particularly to a paper multi-sheet having an effect of increasing the soil temperature which cannot be expected from conventional paper multi-sheets.

[0002]

2. Description of the Related Art Multi-sheets for agriculture and gardening are
Used for weed control, heat retention and soil moisture retention. Conventionally, plastic films such as polyolefins have been used in this field, but since these film mulches have almost no biodegradability, it is necessary to recover the used film after use, and this recovery work is necessary for farmers and users. It is a burden.

On the other hand, many proposals have been made for paper multi-sheets, taking advantage of the fact that paper rots and decomposes in the soil. For example, JP-A-55-111734 discloses a method of impregnating paper with a black colorant as a method of imparting heat retention to a paper multi-sheet. Further, JP-A-60-250949 discloses a method of coating paper with polyvinylidene chloride and carbon black. However, the paper mulch sheet is inferior to the film mulch in terms of heat retention because of its high air permeability and moisture permeability.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to provide a paper mulch having an effect of increasing the ground temperature. At the same time, the present invention provides a paper multi-sheet that has excellent workability during the spreading of the paper multi-sheet and has its weather resistance and decay resistance adjusted appropriately.

[0005]

Means for Solving the Problems The present invention provides (1) a paper multi-sheet, characterized in that it has a moisture-proof layer containing latex and wax as main components on one side of a base paper mainly made of natural pulp. (2) The base paper of a paper multi-sheet contains oxyquinoline or a derivative thereof or a salt thereof and / or humic acid or a salt of humic acid and a divalent or higher cation, (1) (3) The paper multi-sheet according to (1) and (2), characterized in that the base paper of the paper multi-sheet (3) has a breaking elongation in the longitudinal direction of 3 to 20%.

The inventors of the present invention have earnestly studied the cause of the paper mulch sheet (hereinafter referred to as paper mulch) having no effect of raising the ground temperature, and have obtained the following findings. That is, since the paper mulch is essentially breathable and moisture permeable, when the soil temperature rises due to solar radiation, underground moisture permeates through the paper mulch and evaporates, and the heat of vaporization is dissipated into the atmosphere. It is hard to go up.

Therefore, the present inventors have found that when a moisture-proof layer is provided on the paper mulch, the water vapor permeability of the paper mulch decreases, and as a result, the effect of increasing the ground temperature comparable to that of the film mulch can be achieved. Was completed.

The present invention will be described in detail below. The base paper used in the paper mulch of the present invention is mainly made of wood pulp and / or waste paper pulp, and if necessary, polyolefin-based synthetic pulp, vinylon binder fiber, polyester fiber or the like is used as a binder fiber, and has a special basis weight. Although not limited, those of 30 to 200 g / m ² are appropriately used. The blending amount of wood pulp and waste paper pulp is not particularly limited, but a high blending ratio of waste paper pulp contributes to cost reduction, but has a drawback of lowering strength.

Binder fibers such as polyolefin-based synthetic pulp, vinylon binder fiber and polyester fiber have no or significantly slower biodegradation rate than natural pulp. The mesh structure of the sheet is maintained.
Therefore, it is possible to slow down the biodegradation rate by increasing the blending amount of the binder fiber, but if the blending amount is excessive, it becomes difficult for the paper mulch to collapse and it becomes an obstacle in the subsequent production. Therefore, the binder fiber content is at most 20%
It is preferably 10% or less, more preferably 10% or less.

In order to impart biodegradation resistance to the buried portion in the ground, oxyquinoline, a derivative thereof, or a salt thereof may be contained. Since oxyquinoline has a bactericidal effect, it is less susceptible to biodegradation when added to paper. Examples of oxyquinoline include 8-oxyquinoline and 2
-Oxyquinoline, dibromo-8-oxyquinoline, dichlor-8-oxyquinoline and the like, and salts thereof are used, but especially 8-oxyquinoline copper is preferably used. These oxyquinolines may be used in an amount of 0.05 to 5% by weight based on the pulp. As a method of addition, a salt of oxyquinoline or a salt of an oxyquinoline derivative may be added to the raw material slurry for papermaking.

The paper mulch is designed to meet the required strength under both conditions of a part which is buried in the ground and is susceptible to biodegradation and a part of the ground surface which is susceptible to deterioration by being exposed to sunlight, rain, wind and the like. I have to. Since humic acid absorbs ultraviolet rays and has water resistance, it is mainly used for imparting weather resistance to a portion exposed to sunlight. Since humic acid and salts of cations having a valence of 2 or more of humic acid are poorly soluble in water, it is preferable to use humic acid salts that are soluble in water for addition to paper. For example, alkali metal salts or ammonium salts such as lithium salt, sodium salt, potassium salt and the like, alkaline earth metal salts such as magnesium salt, calcium salt and the like can be used, and preferred are sodium salt and ammonium salt. is there. Humic acid or a salt of humic acid and a cation having a valence of 2 or more may be used in an amount of 0.05 to 5% by weight based on the pulp.

After the water-soluble humic acid salt is added to the slurry, a water-soluble polyvalent metal salt having a valence of 2 or more is added to form a metal chelate, which is adsorbed on the pulp. As the water-soluble polyvalent metal salt having a valence of 2 or more, for example, aluminum sulfate is suitable.

The spreading of the multi-sheets on the field is performed by hand tension or by using a cultivator. In the case of a cultivator, a device called mulcher, which is used for ridge formation and spreading, is connected to the rear of the cultivator. This is done by pressing the multi-sheet to the ridges with the rollers of, and placing the soil dug up by the cultivator on both sides of the ridges as weights. At this time, the multi-sheet is vertical,
Since the film is stretched in the lateral direction and the film sheet has a large elongation, there is no problem, but the paper mulch sheet may be broken, and the stretchability of the paper mulch is important. The elongation is 3 to 20 if it is expressed by tensile elongation at break.
%, Preferably 5% or more. Since a large tensile load is not applied when mulching by hand,
There is no problem even if the longitudinal elongation of the paper is less than 3%. As a method for imparting extensibility to the paper multi-sheet, crepe processing or so-called curpack processing in which the paper multi-sheet is shrunk finely on a paper machine used for producing kraft stretched paper may be used.

The moisture-proofing agent is not particularly limited as long as it is a combination of a latex and a wax capable of imparting moisture-proofing and waterproofing properties to the paper after coating, and examples thereof include styrene-butadiene latex, methylmethacrylate-butadiene latex and acrylonitrile-. At least one of latexes such as butadiene latex is mixed with a wax emulsion such as paraffin wax emulsion or polyethylene wax emulsion. The moisture-proof mechanism using latex and wax is said to prevent the permeation of water vapor by filling the gaps between the latex particles with the wax particles and further coating the surface of the coating film with the wax particles.

The coating amount of the moisture-proofing agent is such that the water vapor permeability (according to JIS Z 0208 (cup method) B method) of the coated base paper is 10.
It is preferable to determine the coating amount so as to be 0 g / m ² · 24 hr or less. With this level of moisture permeability, evaporation of soil moisture can be suppressed to a low level.

The paper mulch of the present invention may be spread by arranging the surface coated with the moisture-proofing agent on the side of the field or vice versa. Since the paper mulch of the present invention has a moisture-proof layer, it has water resistance, and as a result, it exhibits the secondary effects of being less likely to deteriorate due to rainfall and having good shape retention. The shape-retaining effect is greater when the surface having the moisture-proof layer is directed outward (to the sky).

The advantage of the paper mulch is that it collapses in the soil if it is plowed into the soil after the crop is harvested. The presence of this moisture-proof layer may cause a delay in disintegration when buried in the soil, but in reality, the coating layer has strength only when it is together with the base paper. Field tests have confirmed that the entire mulch will collapse.

As the coating equipment for the moisture-proof layer, any of an air knife coater, a bar coater, a roll coater, a blade coater and the like can be selected for coating, but if continuous coating of latex and wax emulsion is continued. An air knife coater is preferable because a bar coater or a blade coater is likely to cause troubles due to color cake.

[0019]

The paper mulch obtained according to the present invention can suppress the evaporation of soil moisture and emits less heat due to the evaporation of moisture, so that the soil temperature can be increased.

[0020]

EXAMPLES In order to make the present invention easier to understand,
Examples are shown below, but the following examples limit the present invention.
Not something. In the text,% means% by weight of solid content. Example 1 After a slurry having the following composition was obtained, papermaking was performed using a Fourdrinier paper machine.
Paper, basis weight 50g / m ² A sheet for paper mulch was obtained. ──────────────────────────────────── Unbleached softwood kraft pulp (Canadian Standard Freeness 350ml) 55% Corrugated board Waste paper 40% Vinylon fiber (fineness 1d, fiber length 3mm) 5% Internal sizing agent (trade name Size Pine E, Arakawa Chemical Co., Ltd.) vs. fiber 1.5% Sodium humate (trade name CHA-02, Ternite) Fiber) 4% 8-oxyquinoline copper 0.2% sulfuric acid band (adjusted to pH 4.5) Appropriate amount ────────────────────────── ─────────── styrene-butadiene copolymer latte
X polymer (polymer glass transition point 20 ° C, Japan
Made by Zeon, solid content 45%) 58% and wax emulsion
(Trademark: OKW-40, Arakawa Chemical, solid content 40%)
A 42% moisture barrier solution was applied with a bar coater.
After that, it is dried at 105 ° C, and the moistureproofing agent is 10 g / m in solid content.
² A coated paper mulch was obtained. Permeability of paper after coating with moisture barrier
Is 46 g / m² ・ It was 24 hours (JIS Z 020
8 (cup method) according to method B).

Example 2 A paper mulch was obtained in the same manner as in Example 1 except that the coating amount of the moistureproofing agent was 8 g / m ² . The water vapor permeability of the obtained paper mulch was 80 g / m ² · 24 hr.

Example 3 A paper mulch was obtained in the same manner as in Example 1 except that the coating amount of the dehumidifying agent was 5 g / m ² . The water vapor permeability of the obtained paper mulch was 120 g / m ² · 24 hr.

Example 4 A paper mulch was obtained in the same manner as in Example 1 except that when the base paper was made, it was shrunk finely on a paper machine and subjected to stretchability imparting processing. The elongation at break in the machine direction of the obtained base paper (before coating with the moisture-proofing agent) was 7.3%, and the water vapor permeability of the paper mulch obtained after coating with the moisture-proofing agent was 52 g / m ² · 24 hr.

Comparative Example 1 A paper mulch was prepared in the same manner as in Example 1 except that the moistureproofing agent was not applied to the base paper. The water vapor transmission rate of the base paper not coated with the moistureproof agent was 2000 g / m ² · 24 hr or more.

Comparative Example 2 A black film mulch having a thickness of 30 μm was used.

Examples 1, 2, 3, 4, Comparative Examples 1 and 2
The sheet obtained in 1 was mulched by hand on the flat ridge shown in the cross-sectional view of FIG. 1 with the surface coated with the moisture-proofing agent facing the field. Mulching was conducted in late June 1994.

[Measurement of the effect of raising the ground temperature] For temperature measurement, a thermocouple was inserted into the ridge at a depth of 5 cm, and the temperature was recorded every 10 minutes. Table 1 shows the results of the maximum and minimum soil temperatures measured in late June. It can be seen that the paper mulch of the present invention has an effect of increasing the ground temperature, although it is slightly less than the black film mulch.

[Determination of weed-preventing effect and shape-preserving ability of paper mulch] In order to observe the decay rate of the obtained paper mulch after mulching, water was sprinkled once every 2 to 4 days after the soil temperature was measured. . As for watering, the amount of rainfall at this time is less than usual,
It went because the decay of the paper mulch was slow. Observe the appearance of the paper mulch after 90 days, keep the shape of the paper mulch,
Table 1 shows that the weed-controlling effect was maintained as ◯, and rot and weeds were shown as x. The paper mulch of the present invention is 90
It can be seen that it retains its shape even after a day and has a weed-proofing effect.

[Measurement of disintegration property of paper mulch sheet in soil] From the paper mulch obtained in Example 1 and Comparative Example 1, length 1
A test piece was cut into a shape with a width of 2 cm and a width of 6 cm, and the test piece was sandwiched with culture soil to a depth of 2 cm above and below and packed in a container with a lid. This culture soil has a water content of 33% ± 1% in advance.
Adjusted to. The container with a lid was adjusted to a temperature of 30 ° C., and the test piece was taken out after a lapse of 3, 5, and 7 days, washed with water, and then the wet tensile strength was measured. The results are shown in Table 2 and FIG. It can be seen that the paper mulch obtained in the present invention does not lose the disintegration property in soil even if it has a moisture-proof layer.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a paper mulch which has an effect of raising the ground temperature which is not present in the conventional paper mulch, and which is excellent in workability at the time of spreading and whose weather resistance and decay resistance are appropriately adjusted. Becomes

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a shape of a ridge according to an embodiment of the present invention.

[Explanation of symbols]

 1: Paper mulch 2: Ground surface

FIG. 2 is a graph showing the soil burial strength of the paper mulch obtained in Example 1 of the present invention and Comparative Example 1. The horizontal axis represents the burial period (days), and the vertical axis represents the burial strength.

Claims (3)

[Claims] 1. A paper multi-sheet, characterized in that a base paper mainly made of natural pulp has a moisture-proof layer containing latex and wax as main components on one side thereof. 2. A paper multi-sheet base paper containing oxyquinoline or a derivative thereof or a salt thereof and / or humic acid or a salt of humic acid and a cation having a valence of 2 or more. Paper multi-sheet. 3. The paper multi-sheet according to claim 1, wherein the base paper of the paper multi-sheet has a breaking elongation in the longitudinal direction of 3 to 20%.